Method for making a medical implant with open-work structure and implant obtained by said method

ABSTRACT

This process comprises the step consisting in forming the structure from a single wire, by running each strand of wire helicoidally from one end to the other of the structure and by interlacing this strand with other strands previously arranged. Said method moreover comprises the steps consisting in:—forming a loop ( 12 ) between each strand ( 11   b,    11   c ) at each end of the structure ( 10 ) and setting the free ends of the first ( 11   b ) and of the last strand significantly back from the ends of the structure ( 10 ).

The present invention concerns a method of production of a medicalimplant with a mesh-like structure, notably of a device for thetreatment of a corporeal duct currently denominated as “stent” or of animplant able to plug a hole in a corporeal wall, currently denominatedas “plug”. The invention also concerns an implant obtained by thismethod.

It is well-known to restore the section of the lumen of a corporeal ductby means of a tubular extension. This extension, currently denominatedas “stent”, is deformable between a contraction state, enabling itsintroduction and its sliding in corporeal ducts up to the site to betreated, and a deployed state, wherein it rests against the wall of theconduit to be treated and restores said section of the conduit. Such astent may also be used for implanting a prosthetic system in a corporealduct, for instance a cardiac valve, or to isolate an arterial hernia.

It is also well-known to plug a hole in a corporeal wall by means of atwo-collar implant, currently denominated as “plug”, each of thesecollars resting against one of the faces of the wall to be treated.

There exist numerous models of stents or of plugs, notably stents formedby laser-cutting a thin sheet of appropriate metal material or formed bybraiding several metal wires, notably made of memory-shape alloy.

The shortcoming of these stents and plugs lies in their being relativelydifficult to produce.

The shortcoming of the stents also lies in their being little adaptableas regards the variations in diameter which they may adopt, so thatstents of different diameter must be produced for treating differentcorporeal ducts, of different diameters.

The shortcoming of the stents made of breaded wires lies moreover intheir being relatively aggressive at their ends, which may havesignificant damaging consequences.

The document EP 0 857 471 describes several structures of stent, whereoftwo, with “trellis mesh” are difficult to produce and exhibit noadaptability of diameter or of shape. This document also describes astent formed by a single wire whereof each strand runs helicoidally fromone end to the other of the stent and is braided to the others strands.At the ends of the stent, each strand connects to the following strandby an elbow.

This structure of stent is considered as solving the shortcomingsaforementioned only partially, particularly which concerns theadaptability of the diameter or of the shape of the stent and thecharacter relatively aggressive of its ends. Besides, the free ends ofthe first and of the last strand appear able to protrude beyond ends ofthe stent when the diameter or the shape of this stent is modified, andbe thus particularly aggressive for a corporeal duct.

The document U.S. 2002/169498 describes a stent with a “trellis mesh”structure, considered as difficult to produce and exhibiting noadaptability of diameter or of shape.

The purpose of the present invention is to remedy all the shortcomingsaforementioned of methods of production of stents according to the priorart.

Its main object is hence to provide a method of production of a medicalimplant with mesh-like structure, notably a “stent” or a “plug”,relatively easy to implement and enabling the realisation of implantswhich are perfectly functional.

Another object of the invention is to provide a method enabling therealisation of a structure whereof the diameter and/or the shape may bevastly adapted to suit the needs.

Another object of the invention is to provide a method enabling therealisation of a stent which, whereas this stent has a given diameter,may be used in a wider range of corporeal ducts.

Another object still of the invention is to provide a method enablingthe realisation of a stent whereof the ends are little aggressive forthe walls of the corporeal duct treated.

The method comprises, in a manner known in itself, the step consistingin forming the structure from a single wire, by running each strand ofwire helicoidally from one end to the other of the structure and byinterlacing this strand with other strands previously arranged.

According to the invention, the method comprises moreover the stepsconsisting in:

-   -   forming a loop between each strand at each end of the structure;        and    -   setting the free ends of the first and of the last strand        significantly back from the ends of the structure.

Thus, the method according to the invention consists in:

-   -   a) using a single wire to form a tubular mesh-like structure;    -   b) forming a first strand whereof the free end is set        significantly back from a first location corresponding to a        first end of the structure to be realised and running this first        strand along a helicoid path up to a second location        corresponding to a second end of the structure to be realised,        this first strand forming a loop at this second location, thus        singling out a second strand;    -   c) running this second strand along a helicoid path up to said        first location, by interlacing this second strand with the first        strand when it meets the latter, said second strand formant a        loop at this first location, thus singling out a following        strand;    -   d) running this following strand along a helicoid path up to the        opposite location, by interlacing this following strand with the        front strand(s) on its way, this following strand forming a loop        at said opposite location, thus singling out a following strand;    -   e) repeating the operations from the step d) above as many times        as necessary to form a mesh-like tubular structure and loops on        the whole circumference of said locations, up to singling out a        last strand;    -   f) interlacing the last strand with the previous strand(s) on        its way, and interrupting this last strand so that its free end        is set significantly back from the opposite location.

Realising a structure from a single wire, combined to the arrangement ofthe loops between each strand of wire and to the setting of the freeends of the first and of the last strand significantly back from theends of the structure, enables to slide the strands against one another,this sliding motion being rendered totally possible by clamping orexpanding loops, according to the diameter or the shape given to thestructure. The latter is thus vastly deformable in its diameter as wellas in its shape, and remains non aggressive for the walls of a corporealduct regardless of the diameter and/or the shape given thereto.

The absence of welded spots between the strands and the deformability ofthe loops also has as an essential advantage to enable significantvariation of the angles formed by the strands therebetween. Themultiples slides of these strands enable wider variability of thedifferent diameters which said structure may exhibit, and hence therealisation of a stent having wider possibilities of variations indiameter, which enable the latter to be used for treating a wider rangeof diameters of corporeal ducts.

The loops formed by the wire at the ends of said structure partake ofthese wider possibilities of deformation and are moreover non aggressivefor the wall of the corporeal duct treated.

The setting of the free ends of the first and of the last strand vastlyback from the ends of the stent enable vast adaptations of the diameterand/or of the shape of the stent without risking that these endsprotrude beyond the ends of the stent and should not form sharpexcrescences for the corporeal duct to be treated.

The structure realised may be used as such as a tubular stent. It thushas a diameter which may vary easily or have a shape easily adaptable tothe conformation of the corporeal site to be treated.

This structure may also be used s a blank for the realisation of a stentor of a “plug” of specific shapes. The method then comprises:

-   -   a step of deformation of the tubular structure obtained,        according to the shape of the stent or of the “plug” to        realised, and    -   a step of further treatment, enabling to stabilise this tubular        structure in this state of deformation.

Preferably, interlacing a strand with the other strands encountered bythis strand is performed as a braiding process, i.e. this strand runsalternately on a strand on its way then under the following strand, andso on.

This braiding confers said structure such a handling that it may be usedas a stent or to serve as a blank for the production of other implants,notably plugs. This braiding enables moreover reliable stop of the firstand of the last strands formed by the wire.

The wire used may notably be a wire made of a shape memory alloy, inparticular the nickel-titanium alloy, known under the designation“NITINOL”.

The diameter of the wire used may range from 0.15 to 0.5 mm.

The diameter of the structures which may be produced by the methodaccording to the invention is very wide, and range from 5 to 100 mm.

The method may contain the step consisting in placing on said structurea means for longitudinal shortening of this structure, able to switchfrom an elongated state to a shortened state.

This longitudinal shortening means enables the deployment of thestructure, or to facilitate this deployment.

This longitudinal shortening means may be an elastic means, for instancea wristband made of elastic matter, notably of silicon; this means mayalso be with shape memory and switch from its elongated state to itsshortcoming state by heating to the temperature of the body further tothe implantation of the structure.

Said longitudinal shortening means may notably be engaged through twoloops formed at the ends of said structure.

The method may moreover contain the step consisting in covering saidstructure of a watertight flexible wall, notably with a Teflon sheetsawed to this structure.

The latter is thus watertight and may isolate an arterial hernia when inplace.

The invention will be better understood, and other characteristics andadvantages thereof will appear, with reference to the appended schematicdrawing, representing, for non limiting exemplification purposes,several structures of implant obtained by the method concerned.

FIGS. 1 to 4 are perspective views of a device used for implementingthis method, showing respectively four successive steps contained inthis method;

FIG. 5 is a perspective view of the mesh-like tubular structureobtained; for clarity of the drawing, this structure is fictitiouslyrepresented as opaque, the portions at the foreground masking theportions at the background;

FIG. 6 is a view of said structure similar to FIG. 5, below anotherangle, the structure being fitted with an elastic wristband forming alongitudinal shortening means;

FIG. 7 is a perspective view of another device used for implementingthis method;

FIG. 8 is a perspective view of this device with placement of amesh-like tubular structure thereon;

FIG. 9 is a view of this mesh-like tubular structure, after retractionoutside the device; here also, this structure is fictitiouslyrepresented as opaque;

FIGS. 10 to 12 are face, side and sectional views, respectively, afterplacing on a corporeal wall, of an implant obtained from the mesh-liketubular structure shown on FIG. 9, this implant being intended forblanking a hole existing in a corporeal wall;

FIGS. 13 and 14 are side and sectional views, respectively, afterplacing on a corporeal wall, of another implant obtained from of themesh-like tubular structure shown on FIG. 9, this implant being alsointended for blanking a hole existing in a corporeal wall; and

FIGS. 15 and 16 are side views of both examples of mesh-like tubularstructures which may be obtained by the method according to theinvention.

For simplification purposes, the portions or element present on thesedifferent devices and structures will be designated by the same numericreferences and will not be described again.

FIG. 1 represents a tubular chuck 1 drilled with holes 2 evenlydistributed on its wall, these holes 2 being aligned longitudinally andtransversally. On its longitudinal ends 1 a, 1 b, the chuck 1 comprisesseries of holes evenly distributed on its circumference, receiving withfrictions, but with removability, cylindrical studs 3.

The chuck 1 comprises moreover a hole 4 provided slightly recessed fromone of its ends 1 b.

The chuck 1 is intended to be used for producing a mesh-like tubularstructure 10 as shown on FIGS. 5 and 6, by means of a single metal wire11. This wire 11 is notably made of shape memory alloy known under thedesignation “NITINOL”.

To produce the structure 10, an appropriate length of wire 11 is cut,for instance four metres, and one end 11 a of wire is attached to thechuck 1 by engagement in the hole 4 and around the end edge of the chuck1 then twisting this end 11 a around itself.

The wire 11 is then run around a stud 3 of the end 1 b slightly offsetangularly, then along the wall of the chuck 1, along a helicoid pathrunning above holes 2 aligned on this path.

The first strand 11 b of wire thus formed runs along the wall of thechuck 1 then is engaged around the stud 3 corresponding to the end 1 a,by forming a loop around this stud 3, thus singling out a second strand11 c.

As shown on FIG. 1, this second strand 11 c is run along the wall of thechuck 1 along a helicoid path until it comes back to a correspondingstud 3 of the end 1 b and form a loop 12 around the latter, thussingling out a following strand 11 d. In the example represented, thenumber of holes 2 and of studs 3 is determined so that this secondstrand 11 c comes back to the stud 3 adjoining the stud 3 around whichis engaged the previous strand 11 b.

As can be deduced from FIGS. 2 and 3, these engagement operations of astrand along the wall of the chuck 1 via a helicoid path, therebyforming a loop 12 around a corresponding stud 3 are repeated as manytimes as necessary for the formation of the tubular mesh-like structure10, visible on FIG. 4 whereas it is practically finished.

Each strand is braided with the others strands on its way, i.e. runsalternately over a strand on its way then below the following strand,and so on. This braiding is facilitated by the holes 2 and by theconformation of the free end 11 e of the wire 11 into a hook.

The last strand is braided with the strands on its way, then the end ofthis strand is cut to the desired length, so that it is set back fromthe corresponding end of the chuck 1, i.e. the end 1 a in the examplerepresented.

The first strand 11 b is then cut to the desired length, so that its endis set back from the end 1 b, then the studs 3 are extracted from theholes which receive said studs in order to free the structure 10 and toenable to remove said studs from the chuck 1 by a sliding motion.

The structure 10 thus constituted does not comprise therefore anywelding spots between the strands of wire 11, nor braids at its ends,but loops 12. The absence of welding spots between the strands and theexistence of these loops 12 enable to slide the strands against oneanother when antagonistic stresses are exerted transversally on thestructure 10, and this sliding enables a significant variation of theangles formed by the strands therebetween and hence of the diameterwhich said structure 10 may acquire.

The latter may be used as such and constitute an extension of corporealduct currently denominated as “stent”. After production asaforementioned, it is exposed in such a case to one or several thermaltreatments enabling to stabilise its form and to confer supra-elasticproperties thereto.

This stent has hence wider possibilities of variations in diameter,which enable it to be used for treating a wider range of diameters ofcorporeal ducts.

The structure 10 may also be deformed to constitute a stent of smalleror of larger diameter, or a stent of particular shape, for instance witha median narrowing. An appropriate contention device, holding thestructure 10 in the shape to obtain before thermal treatment, is used ineach case, i.e. a contention tube for the production of a stent ofsmaller diameter, a chuck of diameter larger than the chuck 1 for theproduction of a stent of larger diameter, or an appropriate shape in theother cases. FIGS. 15 and 16 show in this view two examples of mesh-likestructures 10A, 10B obtained by braiding on a chuck of appropriate shapeor by deformation of the structure 10 then thermal treatment thereof indeformed condition, i.e. a structure 10A whereof one end is flared and astructure 10B whereof the median zone is bulged. The structure 10A maynotably serve as a stent for treating a Fallot tetralogy, and thestructure 10B may notably serve as an aortic stent for placing an aorticvalve, the bulged zone being adaptable to the Valsalva sinus.

FIG. 6 shows a structure 10 obtained as described previously, whereonhas been placed a wristband 13 made of silicon, engaged through twoloops 12 substantially aligned longitudinally. This wristband 13 iselastic and is stretched when the structure 10 is in a radialcontraction condition, taking into account the closing of the anglesformed by the strands therebetween during this contraction, and hencethe increase in length of the structure 10. When this contraction isreleased, when placing the implant formed by this structure, thewristband 13 tends to regain its non-stretched shape, as shown by thearrows 15. This wristband 13 provides consequently, and readily, alongitudinal shortening means of said structure 10, which enables orpromotes the deployment of this structure 10.

FIGS. 7 to 9 show a chuck 1 designed to enable the production of astructure of stent 10 shown on FIG. 9, comprising a central narrowing17.

The chuck 1 comprises in this case two portions 20 of longitudinal endsof larger diameter and a median portion 21 of smaller diameter. Theportions 20 comprise the holes 18 receiving the studs 3.

One of the portions 20 is dismountable with respect to the portion 21,to enable retraction of the structure 10 obtained outside the chuck 1.

A structure 10 as shown on FIG. 5 is placed on this chuck 1, the lengthof the latter being such that the strands extend loosely between thestuds 3 to enable the arrangement of said narrowing 17. The loops 12enable perfect maintenance of the structure 10 on the chuck 1 by meansof the studs 3.

One or several contention wires 22 is then used to form the narrowedmedian portion 17 of the structure 10, as shown on FIG. 8, to shape thestent adequately and to keep its shape during the single or varioussubsequent thermal treatments.

The stent thus obtained is notably intended to place a prosthetic valvein a corporeal duct. It is covered with a watertight sheet, notably madeof Teflon.

The structure 10 with narrow portion 17 shown on FIG. 9 may also serveas a blank for the production of implants 23, 24 as shown on FIGS. 10 to14.

The implant 23 is of the type currently designated as “plug”, liable toplug a hole in a corporeal wall 100, notably an interventricular hole ina heart. It comprises to this end a median portion 25 intended to beengaged in said hole, one or two collars 26 adjoining this centralportion 25, liable to rest against said wall 100, on both sides thereof,and a material sheet blanking the opening formed by the median portion25, notably a Teflon sheet.

In the case of this implant 23, shown on FIGS. 10 to 12, both endportions of the structure 10 are folded radially towards the outside ofthis structure, to form both collars 26. This deformation is madepossible by the deformation properties of the structure 10 detailedpreviously. The structure 10, thus deformed, is placed in a contentiontemps, holding it in this position in order to carry out the single orvarious thermal treatments aforementioned.

FIG. 12 shows that the implant 23 may receive one or several elasticclips 27 maintaining both collars 26 on both sides of the wall 100.

The implant 24 shown on FIGS. 13 and 14 is, for its own part, designedfor receiving a prosthetic valve and enabling its assembly on a wall orsimilar corporeal zone. In this case, a portion 10 a corresponding toslightly less than the longitudinal half of the structure 10 is foldedon the other portion 10 b of this structure 10 then is folded radiallytowards the outside at its portion of free end 10 c, to form thus one ofboth collars 26. The end portion 10 d of the other portion 10 b of thestructure 10 opposite portion 10 a is folded radially towards theoutside, and enables to form the other collar 26.

As previously, the structure 10 thus deformed is placed in a contentiondevice which maintains it in this shape and is then exposed to a singleor to various appropriate thermal treatments stabilising its shape andconferring super elastic properties thereto. The implant 24 receivesalso a watertight sheet which covers said implant, notably made ofTeflon.

As appears from the foregoing, the invention provides a method ofproduction of a medical implant with mesh-like structure, notably of a“stent” or of a “plug”, relatively easy to implement and enabling therealisation of implants 10, 23, 24 remaining perfectly functional.

It goes without saying that the invention is not limited to theembodiment described above for exemplification purposes but it extendsto all the embodiments covered by the claims appended thereto.

1. A method of production of a medical implant (10,23,24) with amesh-like structure, notably of a device for the treatment of acorporeal duct currently denominated as “stent” or of an implant able toplug a hole in a corporeal wall, currently denominated as “plug”,comprising the step consisting in forming the structure from a singlewire, by running each strand of wire helicoidally from one end to theother of the structure and by interlacing this strand with other strandspreviously arranged: wherein the method moreover comprises the stepsconsisting in forming a loop (12) between each strand at (11 b, 11 c) ateach end of the structure (10); and setting the free ends of the first(11 b) and of the last strand significantly back from the ends of thestructure (10).
 2. A method according to claim 1, characterized in thatit comprises: a step of deformation of the tubular structure (10)obtained, according to the shape of the stent or of the “plug” torealised, and a step of further treatment, enabling to stabilise thistubular structure (10) in this state of deformation.
 3. A methodaccording to claim 2, characterized in that said step of deformation ofthe tubular structure (10) obtained consists in reducing the diameter ofthis structure (10), for obtaining a stent of a smaller diameter thanthat of this structure (10).
 4. A method according to claim 2,characterized in that said step of deformation of the tubular structure(10) obtained consists in increasing the diameter of this structure(10), for obtaining a stent of a larger diameter than that of thisstructure (10).
 5. A method according to claim 2, characterized in thatsaid step of deformation of the tubular structure (10) obtained consistsin making at least one narrowing of this structure (10).
 6. A methodaccording to claim 2, characterized in that said step of deformation ofthe tubular structure (10) obtained consists in folding at least one endpart of this structure (10), radially towards the outside, to form atleast a substantially flat collar (26), said tubular structure (10)obtained thus permetting to make an implant (23, 24) able to plug a holein a corporeal wall.
 7. A method according to claim 1, characterized inthat interlacing a strand with the other strands encountered by thisstrand is performed as a braiding process, i.e. this strand runsalternately over a strand in its way then under the following strand,and so on.
 8. A method according to claim 1, characterized in that thewire (11) used is a wire (11) made of a shape memory alloy, inparticular the nickel-titanium alloy, known under the designation“NITINOL”.
 9. A method according to claim 1, characterized in that thediameter of the wire (11) used ranges from 0.15 to 0.5 mm.
 10. A methodaccording to claim 1, characterized in that it comprises the stepconsisting in placing on said structure (10) a means (13) forlongitudinal shortening of this structure (10), able to switch from anelongated state to a shortened state.
 11. A method according to claim 1,characterized in that it comprises the step consisting in covering saidstructure (10) with a watertight flexible wall.
 12. Implant with amesh-like structure as obtained by the method according to claim
 1. 13.A method according to claim 2, characterized in that interlacing astrand with the other strands encountered by this strand is performed asa braiding process, i.e. this strand runs alternately over a strand inits way then under the following strand, and so on.
 14. A methodaccording to claim 3, characterized in that interlacing a strand withthe other strands encountered by this strand is performed as a braidingprocess, i.e. this strand runs alternately over a strand in its way thenunder the following strand, and so on.
 15. A method according to claim4, characterized in that interlacing a strand with the other strandsencountered by this strand is performed as a braiding process, i.e. thisstrand runs alternately over a strand in its way then under thefollowing strand, and so on.
 16. A method according to claim 5,characterized in that interlacing a strand with the other strandsencountered by this strand is performed as a braiding process, i.e. thisstrand runs alternately over a strand in its way then under thefollowing strand, and so on.
 17. A method according to claim 6,characterized in that interlacing a strand with the other strandsencountered by this strand is performed as a braiding process, i.e. thisstrand runs alternately over a strand in its way then under thefollowing strand, and so on.
 18. A method according to claim 2,characterized in that the wire (11) used is a wire (11) made of a shapememory alloy, in particular the nickel-titanium alloy, known under thedesignation “NITINOL”.
 19. A method according to claim 3, characterizedin that the wire (11) used is a wire (11) made of a shape memory alloy,in particular the nickel-titanium alloy, known under the designation“NITINOL”.
 20. A method according to claim 4, characterized in that thewire (11) used is a wire (11) made of a shape memory alloy, inparticular the nickel-titanium alloy, known under the designation“NITINOL”.